Small and compact wave gear devices are used as reducers in drive mechanisms such as machine tools and robot hands. A wave gear device is configured from three components: a rigid internally-toothed gear, a flexible externally-toothed gear, and a wave generator, the rigid internally-toothed gear and the flexible externally-toothed gear being supported to be capable of rotating relative to each other via a bearing. The main known examples of wave gear devices are those known as cup-type devices in which the flexible externally-toothed gear has a cup shape, those known as silk-hat-type devices in which the gear has the shape of a silk hat, and those known as flat-type devices in which the gear has a cylindrical shape.
Patent Document 1 (JP-A 2001-336588) discloses a cup-type wave gear device, Patent Document 2 (JP-A 09-280325) discloses a silk-hat-type wave gear device, and Patent Document 3 (JP-A 2009-156461, FIG. 6) discloses a flat-type wave gear device. In Patent Documents 1 and 2, a mechanism is disclosed in which a cross roller bearing is used to support a rigid internally-toothed gear and a flexible externally-toothed gear to be capable of rotating relative to each other.
In Patent Document 4, the applicant proposes a composite roller bearing that can bear loads in the radial direction and in the thrust direction.